This invention has to do with thermal protectors in which a polymeric PTC element, of the heating cable type, for example, is used. Thermal protectors of this type are already known, in which terminals are soldered to conductive foil bonded to opposite broad sides of a flat strip of PTC material. The disadvantages of such a construction are that it is labor intensive and requires careful control, that is more or less limited in its range of response times, and that is liable to have its characteristics affected by shear or tension forces applied to the PTC material, because the connection between the two terminals is made mechanically through the PTC material itself. Compressive forces have little effect upon the thermal characteristics of polymeric PTC material, compared with shear and tensile forces, at least within the limits of compressive force required in the device of this invention.
One of the objects of this invention is to provide a thermal protector that is effective, has uniform thermal characteristics, can be made with a wide range of thermal responses, and can be manufactured in high volume at low cost, automatically.
Other objects will become apparent to those skilled in the art in the light of the following description and accompanying drawing.